Structural mechanism of TRPM7 channel regulation by intracellular magnesium

Abstract

Zn2+, Mg2+ and Ca2+ are essential divalent cations implicated in many metabolic processes and signalling pathways. An emerging new paradigm is that the organismal balance of these cations predominantly depends on a common gatekeeper, the channel-kinase TRPM7. Despite extensive electrophysiological studies and recent cryo-EM analysis, an open question is how the channel activity of TRPM7 is activated. Here, we performed site-directed mutagenesis of mouse TRPM7 in conjunction with patch-clamp assessment of whole-cell and single-channel activity and molecular dynamics (MD) simulations to show that the side chains of conserved N1097 form an inter-subunit Mg2+ regulatory site located in the lower channel gate of TRPM7. Our results suggest that intracellular Mg2+ binds to this site and stabilizes the TRPM7 channel in the closed state, whereas the removal of Mg2+ favours the opening of TRPM7. Hence, our study identifies the structural underpinnings through which the TRPM7 channel is controlled by cytosolic Mg2+, representing a new structure–function relationship not yet explored among TRPM channels.

Structural mechanisms of TRPM7 activation and inhibition

“…To study TRPM7 gating, we introduced the gain-of-function mutation N1098Q 47 . The high constitutive activity of this version of TRPM7 can be readily detected in patch-clamp recordings before the depletion of the negative regulator of the channel, intracellular free magnesium 47 .…”

“…To study TRPM7 gating, we introduced the gain-of-function mutation N1098Q 47 . The high constitutive activity of this version of TRPM7 can be readily detected in patch-clamp recordings before the depletion of the negative regulator of the channel, intracellular free magnesium 47 . Indeed, immediately after establishing the whole-cell configuration, currents recorded from HEK 293T cells expressing TRPM7-N1098Q had much higher amplitude than cells transfected with wild-type TRPM7 (Fig.…”

“…The narrowest point of the pore (~1.4 Å) was formed by four tyrosines Y1085 (one per subunit), which pointed their benzene ring-containing side chains toward the pore center. Emphasizing the importance of these tyrosines for TRPM7 function, substitutions of Y1085 with either phenylalanine or serine resulted in loss-of-function effects 47 .…”

TRPM7 kinase is required for insulin production and compensatory islet responses during obesity

“…Cell culture. Mouse WT and kinase-dead TRPM7 in pIRES-EGFP vector were reported previously (65). MIN6 cells were generously provided by Prof. Per-Olof Berggren and Dr. Barbara Leibiger, Karolinska Institute, Stockholm, Sweden.…”

Promoter methylation of transient receptor potential melastatin-related 7 (TRPM7) predicts a better prognosis in patients with Luminal A breast cancers

“…The TRPM7 ion channel is involved in various physiological and pharmacological processes both with its channel activity and its kinase activity [15,17]. The crucial role of TRPM7 in the balance of Zn(2 +), Mg(2 +), Ca(2 +) implicated in many metabolic processes and signalling pathways [18][19][20][21]. Through its varied physiological roles, TRPM7 is of major importance in much human pathology in various cancers, including breast cancer [22][23][24].…”